I have enough RediMags to equip all 3 of my AR15s if need be, as it stands now though only 1 of my 3 have a RediMag installed right now.
The thing I like about them is that the spare mag is right there at my hands to reload just like that with a mag cinch but I don't have to worry about magazine length to use the RediMag. I can use 5, 10, 20, 30s, 40s and be just fine. Not like if you clip to mags together and have 60 rounds total weight being held in place by the mag catch alone, kinda similar to how a drum mag might stress the mag catch.
I also like the fact that I can carry mags in a standard 3 mag pouch and always refresh the RediMag when given the opportunity. Something I never liked about mags when clipped together is that you often can't use a standard 3 mag pouch or you reduce it's capacity.
I've never really noticed much of a balance offset with my RediMag while using it, just grown accustomed to it over the years. Probably somewhat offsets the Surefire 500A dedicated housing anyhow which hangs off the opposite side of the rifle.
What I don't like about the RediMag, they can be noisy. Aluminum/steel mags held in the RediMag are not held in void that is to as tight as tolerances as that of the magazine well of the rifle. Inserting a magazine into the rifle itself and there is very little noise of the magazine when locked and loaded. But the magazines held in the RediMag generally make a bit of a "slap" noise that can throw noise dispipline right out the window if such a thing is of importance.
Also, I have had 1 RediMag that needed a little bit of fine tuning to get it to retain the magazines well enough. Had one that would drop the spare magazine through the course of firing, wound up that the mag catch was not very thick and wouldn't seat properly into the notch in the magazine.
On a whole, my casual/general use rifles have had the RediMags stripped off of them to keep things simple. Have used them quite a bit though and they've worked well for me when I've used them, going on 4+ years now using them for everything from shooting squirrels out in the field to using them in action rifle matches.